1. Field of the Invention
The present invention relates to a cam lever operated expansion plug, and more particularly, to a cam lever expansion plug which can be locked by fastening the cam lever.
2. Background and Related Art
A typical expansion plug comprises an expandable rubber stopper, and some type of means for expanding the rubber stopper, which operates as the opening and closing apparatus. To operate the expansion plug, the closing apparatus is activated to compress the rubber stopper which expands radially to plug and seal an opening.
U.S. Pat. No. 2,292,149 to Moeller discloses a typical expansion plug having a cam lever closing apparatus. U.S. Pat. No. 2,773,619, also to Moeller, discloses a typical expansion plug having a screw-type handle closing apparatus.
Expansion plugs were later adapted to provide adjustability and to prevent accidental tampering or removal. U.S. Pat. No. 2,822,103 to Moeller describes a cam lever operated plug having a lever locking means which prevents the lever from accidental rotational when in the engaged location. U.S. Pat. No. 2,822,108 to Moeller discloses a plug having an adjustable lock wherein a lock plate holds the plug in a predetermined set position irrespective of the movement of a cam lever. Thus, the cam lever may be rotated without affecting the seal. U.S. Pat. No. 3,295,712 to Peterson describes an adjustable and improved safety plug having a ribbed stem. A U-shaped locking plate may be inserted between the ribs of the stem to maintain a desired seal even if the closing apparatus is accidentally released.
Expansion plugs have proved excellent closure mechanisms due to their air-tight closure characteristics. However, as applications requiring more security have arisen, for example in fuel tanks of aircraft, expansion plugs have been less frequently used. The inventors of the present invention have recognized a need to fasten the expansion plugs in a tamperproof way in order to prevent removal. Moreover, the inventors have recognized a fairly simple and straightforward manner of doing this.
The prior art has never devised a quality means for making the device tamper proof. Although the prior art teaches means for preventing a cam lever from rotating, and means for preventing accidental release, the teachings only go to preventing accidental rotation or release. Deliberate attempts to remove a plug would almost always be successful when using the prior art structure, as they are designed to allow manual release, so that access to the plugged area could be obtained. Thus, conventional expansion plugs tend not to prevent deliberate tampering, for example, theft of gasoline, or terrorist activities by tampering with the gasoline.